Many varieties of solar heating systems have been developed in an effort to reduce the use of gas, oil, electric and other such heat sources. While systems have been used for water heating, space heating, and the like, the solar heating systems tend to be difficult to install, and somewhat complex. Much of the difficulty with the solar heating systems resides in the fact that most of the systems attempt to rely almost exclusively on solar radiation and require intense radiation. Various storage means have been developed to store excess heat when available for use when solar radiation is not available. Another large difficulty resides in the use of water or other heat transfer liquid, or a refrigerent such as a halogenated hydrocarbon, as the heat transfer medium. The use of a liquid, or a gas under pressure, renders the system difficult and expensive, requiring one to design the system carefully to prevent leaks and protect the system from temperatures outside the operating range of the heat transfer medium utilized.
Some prior art solar heating systems have used electric heating to boost, or supplement, the solar heating system when the required solar radiation was not available, but these systems have used heaters large enough to provide all the desired heat. The advantage of such a system is supposedly that the electric heat would be used at night when the load on the electric utility is minimal. Nevertheless, such a system will use a large amount of electric energy when there is insufficient solar radiation available.